Which is more attractive to juvenile fish: availability of food or the complexity of habitat in the mangroves of Bonaire, NA?

Habitat selection is critical to the development, growth and reproductive success for most marine animals. Organisms select habitat based on food availability, as in gulls of the North Sea, complexity of structure, as in juvenile fish of seagrass beds, or a combination of both factors as in marine snails of the rocky intertidal zone. Mangrove forests are known to be important habitat and nursery grounds for many endangered and/or economically important species of fish. These habitats are currently under threat by coastal development and overexploitation, therefore, scientifically supported restoration efforts are currently being pursued. The mangroves of Bonaire are threatened by development, causing hypersaline conditions and change in water flow. In this study food availability and composition as well as the structural complexity of the mangrove prop root system were assessed as possible attractants to juvenile fish. Snorkeling observations along permanent transects of the fishes in and amongst the prop roots as well as the algae and invertebrates living on the prop roots were conducted to establish a baseline understanding of the mangrove community (consumers and prey). In order to assess the impacts of consumers on prop root epibiota, consumers were excluded from prop roots using plastic mesh and the regrowth of preferred food species was monitored. The caging experiment showed evidence of the impacts of herbivores in the mangroves as green algae growth increased significantly in their absence and growth of red algae decreased. Artificial mangrove units (AMUs), modeled after prop roots, were also constructed for this study to test the attractiveness of structural complexity to resident fish. Comparisons between the behavior of the fish community of mangrove prop roots and that of AMUs indicated that there is no distinguishable preference between predators and consumers for structurally complex habitat, but that both prefer more complex habitat over simple structure. The data collected concerning preferred food and habitat structural complexity could be used in restoration projects.

This student research was retrieved from Physis: Journal of Marine Science V (Spring 2009)19: 20-26 from CIEE Bonaire.